This research program explores the novel hypothesis that many of the processes by which we produce and understand language also place high demands on and receive contributions from the hippocampal declarative memory system. This system is uniquely positioned to access and integrate discourse, contextual and experiential information that the language processing system relies on to resolve ambiguity and create meaning. Recent provocative work extends the traditional view of declarative memory as contributing exclusively to long-term memory, to include a critical role in the generation and use of on-line representations, created during ongoing and online information processing to support behavioral performance in the moment. The proposed studies build upon a set of exciting preliminary findings revealing language deficits at low levels of language processing (i.e., within a single noun phrase), and in the absence of any explicit demands on memory (e.g., no delays; when all the stimuli remain in view) in patients with severe and selective declarative memory impairment. Our studies are built around investigating three key areas of language processing where proposals of the memory determinants are central, but untested: Aim 1: To investigate the demands of interactive dialogue on declarative memory; Aim 2: To investigate the demands of referential processing on declarative memory; Aim 3: To investigate the demands of accommodation of talker variability on declarative memory. Our experimental approach capitalizes on a compelling opportunity to combine the study of patients with hippocampal amnesia with eye tracking and behavioral measures to examine the necessity of a form of memory in meeting the demands of language. We will therefore be uniquely able to determine the contributions of hippocampus and declarative memory to language processing and use across multiple levels of language production and comprehension providing crucial tests of hypothesized roles for memory in language use. Language disruptions are common in many neurological and psychiatric conditions where impairments in declarative memory are also prominent, including stroke, traumatic brain injury, Alzheimer's disease, and schizophrenia. Thus, our efforts to characterize the observed language deficits and link them to underlying memory mechanisms are necessary for understanding the broader neural network and cognitive processes that support language use and for developing more sensitive assessments and effective interventions. This application, and the findings generated, offers unparalleled insights and advancements for theories of language processing, clinical service delivery to individuals with concomitant disorders of language and memory, and understanding the organization and operation of language in the brain. PUBLIC HEALTH RELEVANCE: Disruptions in language use are prevalent, debilitating, and costly in numerous neurological and psychiatric diseases where declarative memory deficits are also prominent. By detailing the demands of language use on the hippocampal declarative memory system and the impact on language functioning following hippocampal damage and declarative memory impairment, our findings will be directly relevant to the understanding, diagnosis, and treatment of these non-aphasic language disorders.